This invention relates to an apparatus designed to increase the rate of evaporation of the contents of a number of test tubes. The evaporation is accomplished either by the imposition of a partial vacuum or by the injection of a stream of gas into a test tube containing the sample.
U.S. Pat. No. 4,003,713 involved a device which used the principle of inducing a partial vacuum to increase the rate of evaporation and also the concept of inducing a stream of gas above the solvent to be evaporated to increase the rate of evaporation. The present invention is an improvement of U.S. Pat. No. 4,003,713. The prior patent required pumping gas through all of the needles every time the device was used and this led to wasted gas if the rack was not full of test tubes. If a vacuum was used the vacuum was imposed through all of the needles regardless of whether the rack was full of tubes. The present improvement allows the operator to either pump gas into, or impose a vacuum only through half of the device. The operator has the option of not using the other half of the device or he can use a different gas in that half. Finally the operator could impose a vacuum in one half and pump a gas into the other half of the tubes.
The prior patent also did not allow for varations in the depth of the needles in the tubes. As a result the operation of the device was not always efficient. The present improvement allows the operator to vary the depth of the needles in the tubes and thus vary the height of the needle above the solvent. Therefore the efficiency of the device would be improved. Also, the present improvement allows the device to be inverted and used as a drying rack for small glassware.